Laidlaw's level of mercury meets federal guidelines

Tuesday

Jan 5, 1993 at 12:01 AM

Filtering improvements at the Laidlaw hazardous waste incinerator have brought mercury levels in the facility's waste water within federal limits, state Department of Health and Environmental Control records show. In a related development, a federal judge in Columbia refused an environmental group's request for an injunction against Laidlaw for past mercury violations in November. The judge also refused Laidlaw's request to dismiss the group's lawsuit, which alleges that DHEC was too lenient on the company during the violation period. An attorney for Friends of the Earth, which filed the lawsuit, said Monday that Federal District Judge Joe Anderson plans to hold another hearing after April 5 to determine whether the case should go to trial. Concentrations of mercury, a toxic heavy metal, in waste water at the Roebuck incinerator have fluctuated widely since 1987, frequently exceeding the permitted level of 1.3 parts of mercury per billion parts of waste water. At one point, the mercury level reached 42 times the allowable concentration. In June, DHEC fined Laidlaw $100,000 and ordered it to reduce the levels of mercury and other hazardous substances in its waste water, which flows into the North Tyger River. In addition to cutting back on the incineration of materials containing mercury, Laidlaw added eight, 270-gallon activated carbon filters to its waste-water treatment system in July. The efforts seem to be working. Laidlaw reported a mercury level of 16.2 parts per billion (ppb) at one point last June, or 12 times the allowable concentration, DHEC waste-water records show. But by November, the last month for which reports are available, the highest concentration for the month had dropped to 1.0 ppb. Karl Chandler, Laidlaw's director of operations, said that despite the apparent success in consistently controlling mercury "excursions," the company plans to install additional filter systems as a precaution. "All I can say is my goal is to never violate the mercury limit again," Chandler said. "We feel we have everything under control to do that." In light of the lower mercury levels, Chandler said Laidlaw will no longer pursue a more lenient mercury level and has no plans to appeal an even lower limit of 1.1 ppb proposed in its waste-water permit renewal. The new permit is still under review. Laidlaw's contention previously was that the site should be subject to mercury limits based on the actual impact on fish in the North Tyger River, rather than on broad formulas applied regionally. A study conducted by RMT Inc. of Greenville for Laidlaw last summer showed accumulations of no more than 0.14 milligrams of mercury per each kilogram of fish tissue - far below the Food and Drug Administration's limit of 1.0 mg/kg. The study also showed the same levels of mercury in fish both above and below the waste-water discharge point, which suggests Laidlaw isn't solely responsible for the river's mercury content. MERCUR.Y01